Recently, communication systems performing communication via communication networks such as the Internet and exclusive lines have become widespread along with requests for reductions in business trip expenses and business trip times. Such a communication system establishes a session for transmitting and receiving content data such as image data and voice data between communication terminals, thereby achieving communication between the communication terminals.
It is known that a teleconference system as an example of the communication system causes a teleconference management system to control a session between teleconference terminals (refer to Patent Literature 1). The teleconference system is configured so that a communication start request or its response is transmitted and received between the teleconference terminals via the teleconference management system. The teleconference management system manages whether each of the teleconference terminals is connected to the management system (online) or not (offline) and determines that, when a teleconference terminal selected as a destination of communication is not connected to the management system, the teleconference terminal is not in a communicable state. This configuration enables the teleconference management system to reject a communication start request without transmitting the communication start request to the teleconference terminal as the destination, thereby reducing the time required for processing.
In conventional teleconference systems, a plurality of teleconference terminals is connected to one teleconference management system. Owing to this configuration, when the number of the teleconference terminals connected to the teleconference management system increases, a large processing load is imposed on the teleconference management system. A method is developed that distributes a load imposed on a server by providing a plurality of servers performing processing as a technique for reducing the load imposed on one server (refer to Patent Literature 2).
However, when a plurality of controllers are provided in order to control a session between communication terminals, each of the controllers becomes incapable of determining whether, when a communication terminal selected as a destination of communication is not connected to the controller, the communication terminal as the destination is in a communicable state based on the state of connection between the communication terminal and the controller. This causes a problem in that the session between the communication terminals cannot be efficiently controlled.